Kirwan, G.M., Schweizer, M. & Copete, J.L. (2015)

Multiple lines of evidence confirm that Hume’s Owl Strix butleri (A. O. Hume, 1878) is two species, with description of an unnamed species (Aves: Non-Passeriformes: Strigidae)

. Zootaxa, 3904 (1), 28–50.